Schistosomiasis (also known as bilharzia, bilharziosis or snail fever) is a parasitic disease caused by flatworms. Larval forms of the parasites, which are released by freshwater snails, penetrate the skin of people exposed to affected water. Symptoms include progressive damage to the bladder, ureters, and kidneys, as well as progressive enlargement of the liver and spleen, intestinal damage, and hypertension.